s390: handle R_390_PLT32DBL reloc entries in machine_apply_elf_rel()
    
    Resolves: bz2041911
    Upstream: git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
    Conflicts: None
    
    commit 186e7b0752d8fce1618fa37519671c834c46340e
    Author: Alexander Egorenkov <egorenar@linux.ibm.com>
    Date:   Wed Dec 15 18:48:53 2021 +0100
    
        s390: handle R_390_PLT32DBL reloc entries in machine_apply_elf_rel()
    
        Starting with gcc 11.3, the C compiler will generate PLT-relative function
        calls even if they are local and do not require it. Later on during linking,
        the linker will replace all PLT-relative calls to local functions with
        PC-relative ones. Unfortunately, the purgatory code of kexec/kdump is
        not being linked as a regular executable or shared library would have been,
        and therefore, all PLT-relative addresses remain in the generated purgatory
        object code unresolved. This in turn lets kexec-tools fail with
        "Unknown rela relocation: 0x14 0x73c0901c" for such relocation types.
    
        Furthermore, the clang C compiler has always behaved like described above
        and this commit should fix the purgatory code built with the latter.
    
        Because the purgatory code is no regular executable or shared library,
        contains only calls to local functions and has no PLT, all R_390_PLT32DBL
        relocation entries can be resolved just like a R_390_PC32DBL one.
    
        * https://refspecs.linuxfoundation.org/ELF/zSeries/lzsabi0_zSeries/x1633.html#AEN1699
    
        Relocation entries of purgatory code generated with gcc 11.3
        ------------------------------------------------------------
    
        $ readelf -r purgatory/purgatory.o
    
        Relocation section '.rela.text' at offset 0x6e8 contains 27 entries:
          Offset          Info           Type           Sym. Value    Sym. Name + Addend
        00000000000c  000300000013 R_390_PC32DBL     0000000000000000 .data + 2
        00000000001a  001000000014 R_390_PLT32DBL    0000000000000000 sha256_starts + 2
        000000000030  001100000014 R_390_PLT32DBL    0000000000000000 sha256_update + 2
        000000000046  001200000014 R_390_PLT32DBL    0000000000000000 sha256_finish + 2
        000000000050  000300000013 R_390_PC32DBL     0000000000000000 .data + 102
        00000000005a  001300000014 R_390_PLT32DBL    0000000000000000 memcmp + 2
        ...
        000000000118  001600000014 R_390_PLT32DBL    0000000000000000 setup_arch + 2
        00000000011e  000300000013 R_390_PC32DBL     0000000000000000 .data + 2
        00000000012c  000f00000014 R_390_PLT32DBL    0000000000000000 verify_sha256_digest + 2
        000000000142  001700000014 R_390_PLT32DBL    0000000000000000
        post_verification[...] + 2
    
        Relocation entries of purgatory code generated with gcc 11.2
        ------------------------------------------------------------
    
        $ readelf -r purgatory/purgatory.o
    
        Relocation section '.rela.text' at offset 0x6e8 contains 27 entries:
          Offset          Info           Type           Sym. Value    Sym. Name + Addend
        00000000000e  000300000013 R_390_PC32DBL     0000000000000000 .data + 2
        00000000001c  001000000013 R_390_PC32DBL     0000000000000000 sha256_starts + 2
        000000000036  001100000013 R_390_PC32DBL     0000000000000000 sha256_update + 2
        000000000048  001200000013 R_390_PC32DBL     0000000000000000 sha256_finish + 2
        000000000052  000300000013 R_390_PC32DBL     0000000000000000 .data + 102
        00000000005c  001300000013 R_390_PC32DBL     0000000000000000 memcmp + 2
        ...
        00000000011a  001600000013 R_390_PC32DBL     0000000000000000 setup_arch + 2
        000000000120  000300000013 R_390_PC32DBL     0000000000000000 .data + 122
        000000000130  000f00000013 R_390_PC32DBL     0000000000000000 verify_sha256_digest + 2
        000000000146  001700000013 R_390_PC32DBL     0000000000000000 post_verification[...] + 2
    
        Corresponding s390 kernel discussion:
        * https://lore.kernel.org/linux-s390/20211208105801.188140-1-egorenar@linux.ibm.com/T/#u
    
        Signed-off-by: Alexander Egorenkov <egorenar@linux.ibm.com>
        Reported-by: Tao Liu <ltao@redhat.com>
        Suggested-by: Philipp Rudo <prudo@redhat.com>
        Reviewed-by: Philipp Rudo <prudo@redhat.com>
        [hca@linux.ibm.com: changed commit message as requested by Philipp Rudo]
        Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
        Signed-off-by: Simon Horman <horms@verge.net.au>
    
    Signed-off-by: Philipp Rudo <prudo@redhat.com>